The device contains a DUC mode and a direct digital synthesis (DDS) mode. The data path mode uses complex (I and Q) data from the JESD interface, interpolates and upconverts it in the DUCs, sums the DUC outputs and generates the analog signal in the DAC. In DDS mode, the DUC NCOs are used directly to generate tones without requiring input data.
The list below summarized how DDS mode differs from DUC mode:
- Interpolation filters are not enabled
- JESD204C interface is not enabled
- NCOs use less power (no complex mixing)
- AMP register supplies unique amplitudes for each DUC (DDS) channel, allowing DDS channels to generate tones to cancel harmonic tones in the DAC output. For example, DDS channel 0 could produce a fundamental tone, channel 1 could produce a tone to cancel HD2, and channel 2 could produce a tone to cancel HD3.
- The JMODE and DUC_L registers are ignored and the SYSREF period constraints imposed by the JESD204C system and interpolation filters are removed. See Table 7-3.